@Kate I love how simple it is to use (and to customize the layout). As for Twitter - it's quite a different platform to Facebook, Pinterest, Tumblr, etc. :-) Sometimes it can feel as if you are talking/tweeting to yourself.
The main thing is to engage: ask questions, retweet, favorite, mention people, MORE than you promote your shop, blog, or anything else. A lot of Etsy sellers are solely tweeting their listings, which doesn't really help.
Find potential customers who you think would be interested in what you sell, or businesses that are similar to yours. Search for hashtag keywords related to what you sell or are interested in.
Share links to helpful information or sites (that are relevant to your business). Building a REAL Twitter following and getting engagement does take time, but I've read that quite a few Etsy sellers get success out of it (especially in terms of shop views).
I see some of you tweets get cut off because of the character limit. Don't forget about the 140-character rule when you're tweeting from FB and Tumblr posts).
@Laura That's great. Automated services for social media can be very useful, but it's definitely good practice to tweet/post yourself as well - makes it more human and engaging :-)